1. Field of the Invention
This invention relates generally to a flow power converter and more particularly to a flow power converter employing a flow-controlled duct to capture both vertical and horizontal components of surge energy from overtopping waves and river flows.
2. Description of the Related Art
Wave power as a means of generating electricity has been the focus of low-key study in the US and Europe for over thirty years, but with little public support. Wave energy flux arises primarily from wind friction at the sea surface and is entirely distinct from the diurnal flux of tidal energy arising from the lunar cycle and from the steady flow of the major ocean currents arising primarily from the several solar heating and cooling cycles. Wave power generation is not a widely employed technology. The world's first commercial wave energy conversion farm, the Agucçadora Wave Park in Portugal, was established in 2006. Public interest in this carbon-free power source is now growing because of recent public concern over the accumulating effects of atmospheric carbon loading on world climate.
Ocean waves are generated from a portion of the wind energy coupled to the ocean surface over large areas and the available wave energy in a local region is greater than the solar and wind energies available in the same area. Wave energy available from U.S. coasts alone exceeds the entire U.S. production of coal-fired electrical power, constitutes a perpetual, renewable energy source, and is perhaps the only carbon-free energy source suitable for replacing carbon-based power production on a very large scale without concomitant environmental effects.
The prior art is replete with wave power conversion proposals. Wave power conversion devices may be generally categorized by the choice of energy capture method used to capture the wave energy. They may also be categorized by choice of location and by choice of power extractor. Types of energy capture methods well-known in the art include point absorber or buoy; surfacing and following or attenuator; terminator with perpendicular alignment to wave propagation; oscillating water column; and overtopping. Location types well-known in the art include shoreline, near-shore and offshore. Well-known types of power extraction systems include: hydraulic ram, elastomeric hose pump, pump-to-shore, hydroelectric turbine, air turbine, and linear electrical generator.
For example, in U.S. Pat. No. 4,622,471, Schroeder proposes a terminator system using a plurality of units with unidirectional intake gates disposed horizontally at one elevation to operate independently to capture wave surges upstream from an input penstock. They are adapted to intercept waves and convert their kinetic energy to drive a turbine. Each gate unit includes a horizontally-hinged movable gate adapted to permit the incoming waves to slide over the upper surfaces of the gates and into the penstock. The penstock back pressure operates to push each gate upward to direct the remaining forward moving wave energy to a higher elevation, thereby increasing the water head in the penstock. Schroeder controls the penstock head by applying the same penstock back pressure to every gate unit, which are accordingly hydraulically coupled to one another (not in hydraulic isolation). Schroeder neither considers nor suggests adapting his wave power converter to an overtopping method that retains the captured water at different head pressures in a plurality of substantially isolated chambers each coupled to a penstock, some by way of a check valve.
As another example, in U.S. Pat. No. 7,040,089, Andersen proposes an overtopping wave power station device of the kind where the waves flow up a ramp provided with fixed openings arranged so that little of the water flowing up the ramp flows down through the openings and water flowing down the ramp flows down through the openings and into storage reservoirs positioned below the ramp and extending horizontally at various elevations. Andersen couples each storage reservoirs to an associated penstock and turbine intake. All turbine outlets are coupled together, thereby equalizing the head pressures. Andersen relies on ramp intake closing devices to reduce water and head losses at the ramp openings to the lower storage reservoirs and neither considers nor suggests adapting his overtopping wave power converter to retain the captured water at different head pressures in a plurality of substantially isolated chambers each coupled to a penstock, some by way of a check valve.
In U.S. Pat. No. 4,216,655, Ghesquiere discloses a wave-operated power plant configured to optimally exploit the horizontal force component from the incoming waves.
Normally, the relation between output and investment grows advantageously with the size of the plant. In many cases, it pays to build large plants. However, a large rotating machine, such as a turbine equipped with a generator, costs more than a number of smaller machines with a corresponding total capacity. Complex systems such as hydraulic control systems, are not well suited to incremental implementation (do not scale up well), and have high costs and risks associated with large installations.
Traditionally, low head water turbines have been of an open type, as exemplified for example by conventional water wheels, and have had extremely low efficiency. Conventional power generation turbines such as Francis turbines and Peleton turbines traditionally require high heads of water to generate the water pressure and velocity required to move the turbine blades. Such arrangements require large high dams, additional flumes and the like, requiring massive capital expenditures. A more efficient class of turbines, such as the Root Turbine, for example, can be economically constructed to operate at the higher efficiencies suitable for low head electric power generation applications requiring closed turbine systems to maintain siphon.
Another well-known challenge is to provide a wave power converter able to tolerate the sometimes volatile conditions of the sea surface. Some practitioners suggest selecting installation sites where the average waves are similar in scope to the extreme waves. Also, the wave power converter must withstand a major storm while also operating with acceptable efficiency during average wave conditions.
These unresolved problems and deficiencies are clearly felt in the art and are solved by this invention in the manner described below.